•Nanostructured transition metal binary deposited on nickel foam was synthesized and fabricated via a nitration process.•The formed 1-D nanoneedle nickel-cobalt nitride electrode offers a favorable ...surface area and active sites for HER.•The HER overpotential of 138 mV at 100 mA•cm−2, and Tafel slope of 67 mV/dec were achieved.•The potential of NH3 electrolysis was 0.71 V, lower than that of water splitting, making the H2 from NH3 easier.
The generation of hydrogen from water electrolysis has been widely studied as a power-to-gas pathway for the change of energy consumption system, and has attracted a lot of scientific interest over the past several decades. However, the sluggish anodic oxygen evolution reaction (OER) leads to high overpotential in the electrolytic process. Therefore, using ammonia electrolysis to replace water splitting was recently considered as an advisable method for getting pure hydrogen, as ammonia electrocatalytic decomposition is thermodynamically more energy efficient than water splitting. Thus, in this work, a nanostructured transition metal binary (rather than the most widely used noble metals) deposited on nickel foam was developed through a hydrothermal method. The nickel-cobalt bimetallic catalyst was then further fabricated through the nitridation process annealed in an ammonia atmosphere at high temperatures to prepare nickel-cobalt nitride, which substantiated an optimal electrochemical performance on hydrogen evolution reaction (HER) in an alkaline ammonia system. The electrochemical tests indicated that the 1D nanoneedle nickel-cobalt nitride electrode offers favorable surface area and active sites leading to the hydrogen evolution onset potential close to zero, the overpotential 74 mV at 10 mA•cm−2, 138 mV at 100mA•cm−2, and the Tafel slope 67 mV/dec. In addition, it also demonstrated an excellent stability in long-term running, with the hydrogen generation rate slightly reduced after 10 h of chronoamperometry measurements. Moreover, the potential of ammonia electrolysis was 0.71 V at 100 mA•cm−2 in a two-electrodes system, lower than that of water splitting, suggesting the hydrogen production from ammonia electrolysis could be a promising alternative to water splitting.
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To enhance the tribological performance of the conventional TiCrN coating, the MoS2–TiCr coatings are deposited onto the TiCrN layer by magnetron sputtering. In general, the MoS2 is implemented to ...enhance the friction reduction performance of the TiCrN coating, while the Ti and Cr are doped to increase the density of the structure and prevent MoS2 from oxidizing. The results reveal that with an increase in the content of Ti and Cr in the MoS2–TiCr top layer, the hardness and the coating–substrate adhesion force of the composite coating increase, respectively, due to the compact top layer. Further, the optimized Ti and Cr doping in the MoS2 top layer greatly enhances the tribological properties of the TiCrN/MoS2–TiCr composite coating with a friction coefficient as low as 0.06 and the wear rate is only 6% of the TiCrN coating. The main reason for the excellent tribological properties of the TiCrN/MoS2–TiCr composite coating is probably due to the recrystallization of the MoS2 in the process of wear.
To enhance the tribological performance of the conventional TiCrN coating, the MoSsub.2–TiCr coatings are deposited onto the TiCrN layer by magnetron sputtering. In general, the MoSsub.2 is ...implemented to enhance the friction reduction performance of the TiCrN coating, while the Ti and Cr are doped to increase the density of the structure and prevent MoSsub.2 from oxidizing. The results reveal that with an increase in the content of Ti and Cr in the MoSsub.2–TiCr top layer, the hardness and the coating–substrate adhesion force of the composite coating increase, respectively, due to the compact top layer. Further, the optimized Ti and Cr doping in the MoSsub.2 top layer greatly enhances the tribological properties of the TiCrN/MoSsub.2–TiCr composite coating with a friction coefficient as low as 0.06 and the wear rate is only 6% of the TiCrN coating. The main reason for the excellent tribological properties of the TiCrN/MoSsub.2–TiCr composite coating is probably due to the recrystallization of the MoSsub.2 in the process of wear.
<正>Objective:To construct and identify recombinant plasmid pUIS3-BLC~+.Methods:The cDNA of B-lymphocyte chemoattractant(BLC) was amplified from the total RNA of spleen tissues by PCR method,and ...were inserted into plasmid of Plasmodium berghei with U1S3 knockout by digestion of restrictive endonuclease and T7 ligation.The recombinant plasmids were screened,and then underwent restriction enzymatic digestion and DNA sequencing.Then the confirmed plasmid was further transfected into COS-1 cells by lipofectamine and the BLC expression was tested by RT-PCR and Western blotting.Results:The cDNA of BLC gene was correctively amplified by RT-PCR and the recombinant plasmid pUIS3-BLC~+ was constructed successfully,which was confirmed by restriction enzymatic digestion and DNA sequencing.RT-PCR and Western blotting also showed the BLC gene expression in COS-1 cells.Conclusions:The recombinant plasmid pUIS3-BLC~+ has BLC expression in COS-1 cells,and is useful for further study on BLC transgene and UIS3 gene knockout in Plasmodium berghei.
N-nitrosodimethylamine（NDMA） precursors consist of a positively charged dimethylamine group and a non-polar moiety, which inspired us to develop a targeted cation exchange technology to remove NDMA ...precursors. In this study, we tested the removal of two representative NDMA precursors, dimethylamine（DMA） and ranitidine（RNTD）, by strong acidic cation exchange resin. The results showed that pH greatly affected the exchange efficiency, with high removal（DMA 〉 78% and RNTD 〉 94%） observed at pH 〈 pk_a-1 when the molar ratio of exchange capacity to precursor was 4. The exchange order was obtained as follows： Ca~（2＋）〉 Mg~（2＋）〉 RNTD~＋〉 K~＋〉 DMA~＋〉 NH_4~＋〉 Na~＋. The partition coefficient of DMA~＋to Na~＋was 1.41 ± 0.26, while that of RNTD~＋to Na~＋was 12.1 ± 1.9. The pseudo second-order equation fitted the cation exchange kinetics well. Bivalent inorganic cations such as Ca~（2＋）were found to have a notable effect on NA precursor removal in softening column test. Besides DMA and RNTD, cation exchange process also worked well for removing other 7 model NDMA precursors. Overall, NDMA precursor removal can be an added benefit of making use of cation exchange water softening processes.
Orthogonal test method can reduce test times, shorten test cycles and find multi-factors optimization scheme quickly. In this study, the operation parameters of PEMFC were optimized by the orthogonal ...experiment method, which met the requirements of the fuel cell parameter optimization test under steady working condition. With the help of four factors and three levels orthogonal table, nine orthogonal experiments were designed to study the influences of fuel cell's operating temperature, gas inlet pressure, relative humidity and oxidant stoichiometric ratio on the performance of PEMFC. On the basis of the polarization curve, local current density distributions and electrochemical impedance spectroscopy (EIS) technologies, the correctness of the conclusions obtained from the orthogonal experiment was verified. In the study, the optimization combinations of the operating parameters in different current density loads are listed. The test results show that, the effect of air stoichiometric ratio on PEMFC performance is the largest under the condition of medium and high current density, while the effect of gas inlet pressure on PEMFC performance is the largest under the condition of low current density. On the other hand, the operating temperature and air RH have little impact on the performance of PEMFC. Furthermore, the mechanism of predominant parameters on the performance of fuel cell is discussed.
•The influence degrees of each parameter on the performance of PEMFC were sorted by the orthogonal method.•Polarization curves and EIS were adopted to verify the conclusions obtained from the orthogonal experiment.•Local current density distribution was used to analyze reasons for the performance in different tests.
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•The selective catalytic oxidation of NH3 (NH3-SCO) at low temperatures was studied.•Mordenite-supported Pt-Au alloy catalysts with various Pt:Au ratios were prepared.•The NH3 ...conversion and N2 selectivity depended on the Pt:Au ratio.•The effect of combination of electron-deficient Pt and electron-rich Au was investigated.•Brønsted acid sites were found to be essential for the selective formation of N2.
The selective catalytic oxidation of ammonia (NH3-SCO) to N2 and H2O at low temperatures was studied to remove low-concentration (50 ppm) NH3 from the air. A series of mordenite (M20)-supported Pt-Au alloy catalysts with different Pt:Au ratios were synthesized and tested in the NH3-SCO. The NH3 conversion and N2 selectivity both depended on the ratio of Pt to Au. The 0.52 wt% Pt84Au16/M20 catalyst showed the highest NH3 conversion (90% at 144 °C) even better than Pt100/M20, which was ascribed to the combination of electron-deficient Pt and electron-rich Au in the alloy nanoparticles. The effects of acid sites on the NH3-SCO were investigated by NaOH treatment of Pt84Au16/M20 catalyst. Results suggested that the acid sites could help to increase NH3 conversion, and that Brønsted acid sites are essential for the selective formation of N2.
Selective catalytic oxidation of ammonia (NH3-SCO) into N2 and H2O is considered to be a promising technique to eliminate NH3 pollution. Various Ag/MnO2 catalysts were prepared and applied to ...low-temperature (especially <100 °C) NH3-SCO. The Ag/MnO2-X (X indicating the calcination temperature) catalyst had a variable Ag size and structure depending on the calcination temperature from 200 to 500 °C. The Ag/MnO2-400 catalyst showed 10% NH3 conversion at 35 °C, and the temperature was 90 °C for the complete removal of 50 ppm NH3. More importantly, the N2 selectivities of NH3-SCO over Ag/MnO2-400 at the temperatures ranging from 30 to 120 °C were higher than 96%. Turnover frequencies of NH3 oxidation, N2 selectivity, and byproducts depended on the Ag size/structure. Ag/MnO2-400 with Ag particles of 2.4 nm diameter had the highest density of Ag particles over rod-shaped MnO2 during the reaction, which would be favorable for the formation of adsorbed NO and NH2NO intermediates to form N2 and H2O.
In order to reveal the distribution characteristics of functional groups and the difference of microcrystalline structure parameters between outburst coal and primary coal, the coal samples inside ...and outside the outburst holes of the Sanjia coal mine were examined. The functional groups and microcrystalline structure parameters of outburst coal and primary coal in the Sanjia coal mine were studied by infrared spectroscopy, X-ray diffraction (XRD) experiment and peak-splitting fitting method. The results showed that the substitution mode of the benzene ring in an aromatic structure was mainly benzene ring tri-substituted, with primary coal of 32.71% and outburst coal of 31.6%. The primary coal contained more functional groups, from which hydrogen bonds can easily be formed, meaning that gas is not easily adsorbed by coal. The aromatic hydrogen rate (fHa) of the outburst coal was 0.271, the aromatic carbon rate (ƒC) was 0.986, the aromaticity I1 was 0.477, I2 was 0.373 and the length of the aliphatic branched chain (ACH2/ACH3) was 0.850. Compared with the primary coal, the aromatic hydrogen rate, aromatic carbon rate and the aromaticity of the outburst coal were higher, indicating that the hydrogen and carbon elements in the aromatic functional groups of outburst coal were higher and that the aliphatic functional group was higher than the aromatic structural functional group. ACH2/ACH3 and maturity (Csd) were slightly lower than those of primary coal, indicating that the coal has more straight chains than side chains, while aliphatic hydrocarbons are mostly short chains and have high branched degree. There were obvious 002 and 100 peaks in the XRD pattern. The d002 and d100 of outburst coal were 3.570 and 2.114, respectively, while the number of effective stacking aromatics was 3.089, which was lower than that of primary coal, indicating that the structure of the dense ring in the coal saw certain changes.
The in-situ segmented cell technique can provide real-time, accurate current density distributions and reflect the uniformity of the internal electrochemical reaction in the fuel cell. In this study, ...the effects of the driving cycle, which is composed of idle condition, accelerated condition and overload condition, on the durability of fuel cell were investigated. Various techniques were applied to investigate the degradation mechanism during driving cycle. The cell was operated at 70 °C with 100% humidification for both electrodes in potential static mode. It was found from the I–V curves that after 200 cycles the performance of fuel cell decreased obviously. With the segmented cell technology, the local current density distributions were obtained. It showed that after 200 cycles, the current density at the inlet region declined the most significantly while that of the middle region was always above the mean current density. Meanwhile, electro-chemical impedance spectroscopy (EIS) results and equivalent circuit method presented changes in structure and material degradation of the MEA. Cyclic voltammetry (CV) and TEM results showed serious electrochemical active surface area (ECSA) decline of cathode catalyst due to Pt dissolution and agglomeration. SEM results revealed serious thickness decrease of the membrane and catalyst layers due to humidification cycles and carbon support corrosion at harsh dynamic driving cycles. These all combined led to the performance degradation.
•The effects of dynamic driving cycles on the durability of fuel cell were investigated with segmented cell technology.•Various techniques were adopted to investigate the degradation mechanism.•The current density at the inlet region declined the most significantly.
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